Patent Application
20150204571
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1. Field of the Invention
The present invention pertains to air-conditioning systems and methods of operating air-conditioning systems. More specifically, the invention pertains to an air-conditioning system that is configured to adjust the duration and timing of opening and closing a ventilation damper so as to maximize the efficiency and/or comfort provided by said air-conditioning system. Preferably the air-conditioning system can operate in at least two modes of operation that include an energy savings mode and a maximum comfort mode.
2. General Background
Modern homes and buildings have increasingly been made more weather tight so as to minimize the energy required to condition the air within such structures. However, such improvements have led to the need to forcibly ventilate such structures to avoid the depletion of oxygen and/or buildup of carbon dioxide and other contaminants within the living spaces of the structures. To this end, the American Society of Heating, Refrigerating & Air-Conditioning Engineers (ASHRAE) has established standards for the amount of fresh air that should be drawn into a structure to maintain sufficient levels of oxygen and avoid buildup of carbon dioxide. The standards take into account the volume or floor space, the quantity of bedrooms, and the number of occupants of such structures. More specifically, ASHRAE 62.2 sets forth the amount of fresh air that must be drawn into a residential structure as a function of how frequently said air is drawn in. Under that standard, if one sixth or more of the required daily fresh air ventilation is brought into a structure every four hour period, only a minimum amount of fresh air is required to be brought in. Conversely, if the structure is ventilated less often than every four hours, more fresh air per day is required to be brought in than would otherwise be required. Thus, if a structure is not ventilated continuously, it is advantageous to ventilate the structure at least once every four hours. That being said, ventilating a structure has disadvantages. Assuming there is an appreciable temperature differential between indoors and outdoors, ventilating counteracts the air-conditioning, thereby requiring additional energy to heat or cool. Moreover, ventilating a structure when the air-conditioning system is not also heating or cooling air can cause discomfort.
To provide ventilation, it is known to provide a fresh air damper that is controlled by an air-conditioning system for drawing or forcing fresh air directly into the air-conditioning system. It is also known to configure such air-conditioning systems to periodically open the damper for fixed intervals of time in an effort to ensure adequate ventilation. Still further, it is known to operatively connect the damper upstream of the air-conditioner's primary blower fan such that the primary blower fan can be used to draw in the fresh air. In an air-conditioning system having variable speed fan, the blower fan may draw in fresh air at different rates depending upon the operating speed of the fan. Thus, such an air-conditioning system may draw in more fresh air than is needed.
An air-conditioning system in accordance with the present invention preferably can be operated in at least two modes. One mode seeks to minimize the total amount of fresh air being brought into a structure so as to minimize the amount of energy used to condition (heat or cool) fresh air. Another mode seeks to minimize the time in which the air-conditioning system draws in fresh air while the system is not heating or cooling air so as to minimize periods of discomfort associate with blowing unconditioned air into living spaces.
One aspect of the invention pertains to a method of operating an air-conditioning system. The air-conditioning system comprises a fan and a ventilation damper for drawing fresh air into a living space. The damper is able to open and close. The method comprises storing data indicative of air flow output of the fan over time. The method further comprises closing the damper based on said data.
In another aspect of the invention, an air-conditioning system comprises a fan and a ventilation damper for drawing fresh air into a living space. The damper is able to open and close. The air-conditioning system is adapted and configured to store data indicative of air flow output of the fan over time, and to close the damper based on said data.
Further features and advantages of the present invention, as well as the operation of the invention, are described in detail below with reference to the accompanying drawings.
Reference numerals in the written specification and in the drawing figures indicate corresponding items.
A preferred embodiment of air-conditioning system 10 in accordance with the invention is shown in
As mentioned above, ASHRAE 62.2 sets forth standards for the amount of fresh air that should be drawn into a living space per day (herein referred to as ventilation). The amount increases if one sixth of the amount is not drawn in each four hour period. The amount is also dependent upon the size of the living space and the number of occupants. The electronic control circuit 16 of the preferred embodiment is configured and adapted such that information indicative of the size of the living space (volume or preferably square footage), the number of bedrooms, the number of occupants (preferably defaults to one person per bedroom plus one extra person), and the percentage of fresh air drawn in as compared to the total fan output when the damper is open can be input by an installer or other person. The percentage of fresh air drawn in as compared to the total fan output is preferably measured by the installer using any of the well-known methods of measuring the same (the fan output is specified and therefore only the ventilation air flow rate has to be measured). Preferably the percentage is measured at maximum blower output or whatever other blower speed draws in the least ventilation air as a percentage. By default, the electronic control circuit 16 is configured and adapted to operate the damper 14 and the fan 12 in manner such that at least one sixth of the required daily amount of fresh air is drawn in every four hour period. However, in accordance with the ASHRAE standards, the electronic control circuit 16 is preferably adapted and configured to allow someone to set the air-conditioning system 10 to ventilate less often. Of course, doing so may be less efficient since more ventilation air would be required. Still, it could reduce the number of times the system ventilates when neither heating nor cooling.
Preferably, the control circuit 16 is configured to allow an occupant to operate the air-conditioning system 10 in at least two primary modes. For purposes of describing the invention, one such mode shall be referred to as an “energy savings mode” and another as a “maximum comfort mode.” A flowchart of the energy savings mode is shown in
The maximum comfort mode of operation is configured and adapted to avoid or reduce periods of ventilating when the air-condition system 10 is not also heating or cooling. In the maximum comfort mode, the control circuit 16 is configured and adapted to open the damper 14 each time there is a call for heating or cooling and to maintain the damper open while the air-conditioning system is heating or cooling, unless the inventory (which is tracked by the control circuit 16), reaches a particular value, which is preferably in excess of a four hour inventory. Preferably that particular value is approximately twice the value of a four hour inventory. The control circuit 16 is configured to close the damper 14 when the heating or cooling terminates. However, if the tracked excess inventory reaches or nears zero (a rare event), the control circuit 16 is configured to open the damper 14 and operate the fan 12 at its continuous ventilation rate until there is a call for heating or cooling. Thus, in the maximum comfort mode, the control circuit 16 opens the damper 14 when the air-conditioning system 10 is heating or cooling, and only rarely is the damper open when air-conditioning system is not heating or cooling.
In addition to the forgoing modes of operation, the control circuit 16 may also be configured to operate the damper 14 in a more conventional manner such as opening and closing the damper 14 on fixed intervals. Thus, it should be appreciated that the air-condition system 10 could have additional modes of operation.
In view of the foregoing, it should be appreciated that the invention has several advantages over the prior art.
As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. Still further, the order in which the steps of any method claim that follows are presented should not be construed in a manner limiting the order in which such steps must be performed, unless such an order is inherent.
